In EPON and GPON systems, an optical line terminal must be able to upgrade remotely the software version of an optical network unit. After all the data blocks of the new software version are received accurately, the optical network unit will immediately restart and automatically activate the new software version. From the perspective of downloading software, the foregoing operation of the optical network unit is proper, but the operation may interrupt user services, particularly voice and video services.
Therefore it is desirable to provide a solution which can address this technical problem.